Method for rolling stainless steel



Feb. 24, 1970 Filed Nov. 20, 196? ZOSPECULAR GLOSS RAT/N PERCENT TOTALREDUCTION IN LUBRICANTS H. L. MURPHY ETAL METHOD FOR ROLLING STAINLESSSTEEL 4 Sheets-Sheet 1 4/28 sus' l I AL 40 INVENTORS. HARRY L. MURPHY,JEROME BREssANELLIE KENNETH E. PIN/VOW A'Horne l I I0 20 0F VA R/OUSVISCOSITY Feb. 24, 1970.

Filed Nov. 20, 1967 20 SPECULAR GLOSS RA TING PERCENT TOTAL REDUCTION INLUBRICANTS H. MURPHY ETAL 3,496,746

METHOD FOR ROLLING STAINLESS STEEL 4 Sheets-Sheet 2 I750 Sus I I l 6'0INVENTORS. HARRY L. MURPHY, JEROME R BRESSANELL/ 8 P/NNOW OF VARIOUS103005177 KENNETH H. L. MURPHY EI'AL METHOD FOR ROLLING STAINLESS STEELFeb. 24, 1970 4 Sheets-Sheet 3 Filed Nov. 20, 1967 Qbm WNW QQN 95 DD\ bkhm m flml lvouanaau .l/V39U3d INVENTORS. HARRY L. MURPHY, JEROME F!BRESSA/VELL/ 8 B KENNETHE.P/NNOW Artorn Feb. 24, 1970 H. L. MURPHY ETAL3,

METHOD FOR ROLLING STAINLESS STEEL Filed Nov. 20, 1967 4 Sheets-Sheet 4HARRY L. MURPHY, JEROME I? BRESSANELL/ 8' KENNET E PIA/NOW Z42 ArrorneUnited States Patent 3,496,746 METHOD FOR ROLLING STAINLESS STEEL HarryL. Murphy, Jerome P. Bressanelli, and Kenneth E. Pinnow, Pittsburgh,Pa., assignors to Crucible Inc., a corporation of New Jersey Filed Nov.20, 1967, Ser. No. 684,214 Int. Cl. B21b 45/02 U.S. C]. 7242 2 ClaimsABSTRACT OF THE DISCLOSURE This invention relates generally to theproduction of stainless steel, and, in particular to a method forproducing stainless steel having a relatively dull surface finish. Inaccordance with the present invention, a dull surface finish is impartedto an initially bright stainless steel surface by subjecting it to arolling operation While it is coated with a lubricant having a viscositygreater than 200 SUS (Saybolt Universal Seconds at 100 F.) preferably400 to 4000 SUS, with the optimum lubricant viscosity being within therange of about 1000 to 2000 SUS. By employing lubricants within theseviscosity limits, 20 degree specular gloss ratings of preferably lessthan 40, and optimally of about 15 to 30, are achieved.

It is well known that stainless steel is used in decorative applicationsbecause of its bright reflective appearance. For instance, it iscustomary in the manufacture of trim for motor vehicles to usebright-finish stainless steel. This material, and consequently trim madetherefrom, is highly reflective of sunlight. Consequently, brightstainless steel trim, particularly when it is located on a motor vehiclewithin the vision of the vehicle operator, as is the case withwindshield wipers, can create a safety hazard by its glare andreflection. To eliminate this hazard, stainlesssteel trim that is Withinthe vision of the vehicle operator is desirably provided with a dullrather than a bright reflective finish.

While some dulled stainless steel has been previously produced by eitherchemical attack of the surface or by physical abrasion, such as grit orglass bead blasting, sanding or by using specially roughened work rollsduring cold rolling, these methods have been proven generally timeconsuming, expensive and in many cases incapable of creating a uniformlydulled surface, which renders the product of inferior quality. As anexample, the use of roughened Work rolls during the last cold-reductionpass imparted to the steel delivers an acceptably uniform surface onlyuntil the rolls become smooth through use. The rolls therefore must beresurfaced frequently, which detracts from the economy of operation inthat alternate sets of Work rolls must be available at the mill, and themill is subject to downtime for the period required to change Workrolls.

It is accordingly the primary object of the present invention to providea new and totally different method for producing flat rolled metalproducts such as stainless steel having a dull surface finish ofimproved uniformity, such being effected with standard rollingapparatus.

A further object of the invention is to provide a method for producing adull surface on stainless steel during cold rolling without requiringspecial processing and apparatus such as the use of chemical agents orroughened work rolls.

A more specific object of the invention is to provide a method forproducing a dull surface on stainless steel by using a high-viscositylubricant on the material during a cold-rolling pass.

Another more specific object of the invention is to produce a dullsurface finish on stainless steel by using a lub- 3,496,746 PatentedFeb. 24, 1970 ricant during a cold-rolling pass having a viscositygreater than about 200 SUS (Saybolt Univesal Seconds at F.) preferably400 to 4000 SUS, with a lubricant viscosity within the range of about1000 to 2000 SUS being optimum for the purpose.

These and other objects of the invention as well as a completeunderstanding thereof may be obtained from the following description anddrawings, in which:

- FIGURE 1 presents a series of curves showing the effect of viscosityand degree of reduction on surface finish of Type 434 stainless steel;

FIGURE 2 presents curves similar to those of FIGURE 1, except that theyrelate to Type 301 stainless steel;

FIGURE 3 shows a series of curves indicating the effect of rolling speedon the degree of dulling achieved at varying degrees of reduction onType 434 stainless steel when using 1750 SUS viscosity lubricant; and

FIGURE 4 presents a series of curves similar to those of FIGURE 3 butWith Type 301 stainless steel.

In the manufacture of stainless steel, it is customary practice tosubject the material to a series of cold reductions and intermediateanneals. During cold reduction, a lubricant of a viscosity of about 35SUS and at most, 100 SUS is employed. Upon emerging from the finalrolling pass, the material is characterized by an extremely brighthighly reflective surface.

We have now found unexpectedly that metal surfaces may be dulled tocontrolled degrees without special equipment by employing during arolling pass a lubricant having a viscosity substantially greater thanthat conventionally used. By way of example, for the purpose ofautomobile trim, 20 degree specular gloss ratings of 40 or less,preferably 15 to 30, and ideally about 20, are desired. We 'have foundthat the surface of stainless steel may be dulled readily to this degreeor more during the final cold-rolling pass by employing a lubricanthaving a viscosity greater than about 200 SUS. Lubricant viscositiesWithin the range of about 1000 to 2000 SUS are considered optimum. Undermost conditions dulling in accordance with our invention is done duringthe final cold-rolling operation.

Any of the well-known natural or synthetic lubricants are suitable foruse in the practice of the invention, so long as the necessaryrequirements with respect to high viscosity are met. For example,natural lubricants such as napthenic-base mineral oils, paraffiuic-basemineral oils, vegetable oils, as Well as the silicone, phosphate ester,and glycol synthetic lubricants may be employed.

Experimental work has shown, as will be described in greater detailhereinafter, that the degree of dulling imparted in the practice of theinvention during cold rolling can be controlled by regulating severalprocessing parameters. Foremost of these parameters is the lubricantviscosity, since it must exceed the previously stated minimum before itis effective as an agent for dulling the surface of the steel.Additionally, the speed of the steel through the rolling mill and thedegree of reduction in the mill will also affect dulling.

The limits with respect to lubricant viscosity have been statedhereinabove and are clearly demonstrated by the curves presented inFIGURES 1 and 2. A lubricant viscosity of about 200 SUS is the minimumthat can be used to produce a dull finish in accordance with ourinvention. Lubricants having a viscosity of about 1000 SUS to 2000provide optimum operation because the desired degree of surface dullingcan be produced with less reduction. Application ditficulties areencountered with lubricant viscosities exceeding about 4000 SUS.

As a specific example of the practice of the invention, Types 434 and301 austenitic stainless steel samples were subjected to cold reductionsusing a napthenic-base mineral oil at viscosities of 1750, 1000, 200 and100 SUS, and 4128 SUS with a parafiinic oil. The percent reduction ateach lubricant viscosity was varied between the limits of about 4 to 42to 55 percent. After rolling under these conditions, the samples weretested and their reflectivity determined in accordance with a 20 degreespecular gloss rating.

The results of these experiments are presented in FIGURES 1 and 2. Itmay be seen from these figures that the degree of dulling generallyincreases as lubricant viscosity and reduction increase. Above about1000 SUS, the degree of dulling does not change drastically inaccordance with viscosity changes. At 100 SUS the desired degree ofsurface dulling could not be achieved.

FIGURES 3 and 4 report the results of Types 434 and 301 stainless steel,respectively, dulled in accordance with the invention. During thesetests 20 degree specular gloss ratings of 15, 20, and 30 were achievedusing a napthenic base mineral oil lubricant at a viscosity of 1750 SUS.As may be seen from the figures, as the rolling speed of the steelthrough the rolling mill increased, less reduction was required toachieve any given degree of dulling. At a rolling speed of about 130 to160 feet per minute, the effect of further rolling-speed increases withrespect to promoting dulling began to diminish.

The above-reported data show that at a lubricant viscosity of 100 SUS,the required dulling could not be achieved within desired reductionlimits. Unexpectedly, when the lubricant viscosity was increased to 200SUS, surface dulling to the desired degree resulted within acceptablereduction limits. When the viscosity was increased to within the rangeof about 1000 to 2000 SUS, specifically 1750 SUS, dulling to the desireddegree was achieved over a wide range of reductions. Dulling wasachieved to the extent desired with lubricant viscosities as high asabout 4000 SUS.

The desired dulling is achieved within the above-stated lubricantviscosity limits by maintaining substantially complete and continuousseparation between the work-roll surfaces and the workpiece surfaceduring rolling. The separating fluid film, under pressure, imprints theworkpiece surface producing a dull appearance. If this separation is notmaintained, brightening or inadequate dulling of the workpiece surfaceswill result; the degree of the brightening effect will increasecorrespondingly with increases in the amount of contact between thesurfaces of the work rolls and workpiece.

It may be seen from the above that by the practice of our invention thesurface finish of stainless steel after final cold reduction may be madedull to any desired degree without requiring any major changes in therolling apparatus over that employed in producing typical bright finishstainless steel. Specifically, it is not necessary to use roughened workrolls to achieve dulling as was typical prior to our invention. Hence,conventional stainless steel processing equipment may be used toalternately produce bright or dull stainless steel depending upon theneeds of the customer.

The 20 degree specular glass rating is conducted in accordance with ASTMTest Method D 523. It is to be understood that the invention has primaryapplication in the dulling during reduction of stainless steel having acharacteristic bright surface finish. However, the invention could alsobe used to further dull, during rolling, stainless steel having aninitially dull surface finish, such as that produced by a picklingoperation.

Although various specific preferred embodiments of the invention havebeen described herein, it will be obvious to those skilled in the artthat other adaptations and modifications may be made without departingfrom the scope and spirit of the appended claims.

What is claimed is:

1. A method for producing a dull surface finish on stainless steelcomprising, subjecting said steel to a coldrolling pass reducing thethickness thereof, and providing a lubricant of a viscosity within therange of about 400 to 4000 SUS at F. between the'surfaces of work rollsemployed during cold-rolling and the steel when the reduction is beingeffected to dull the surface of said steel, said lubricant maintainingsubstantially complete and continuous separation between the work rollsand steel during reduction.

2. A method according to claim 1 wherein the lubricant viscosity iswithin the range of about 1000 to 2000 SUS.

References Cited UNITED STATES PATENTS 1,732,065 10/1929 Richards 72-422,151,285 3/1939 Toussaint 72-42 2,938,262 5/1960 Barker et al. 72-42CHARLES W. LANHAM, Primary Examiner E. M. COMBS, Assistant ExaminerUNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,496,746 Dated February 24, 1970 Harry L. Murphy et a1 Inventor(s) Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

After the title, names of the inventors and their addresses, pleasechange the as signee "Crucible Inc. Q a corporation of New Jersey". to--Crucib1e Inc. a corporation of Delaware--.

SIGNED AND SEALED AUG 251970 Edwin-m k mm I. mm. .13. m Gonmissioner ofPatents FORM PC4050 (10-6 uscoMM-oc G0'i76-F'69 i U 5. GOVERNMENTPRINTING OFFICE II. 0-360-134

